Non-reciprocal waveguide phase shifter having side-by-side ferrite toroids



Aug. 11, 1970 J'. P. AGRIOS ETAL I NON-RECIPROCAL WAVEGUIDE PHASESHIFTER HAVING SIDE-BY-SIDE FERRITE TOROIDS Filed Sent. 16. 1968 FIG. 2

, INVENTORS,

JOHN R AGRIOS 8 RICHARD A. STERN.

Assm:

ATTORNEYS.

United States Patent O NON -RECIPROCAL WAVEGUIDE PHASE SHIFTE HAVINGSIDE-BY-SIDE FERRITE TOROIDS John P. Agrios, Long Branch, and Richard A.Stern,

.Manasquan, N.J., assignors to the United- States of America asrepresented by the Secretary of the Army Filed Sept. 16, 1968, Ser. No.759,975 Int. Cl. H01p N32 US. Cl. SSS-24.1

ABSTRACT OF THE DISCLOSURE A non-reciprocal phase shifter utilizing twotoroid ferrites positioned in spaced relationship longitudinally withina section of waveguide. The toroid ferrites are spaced from the top andbottom Walls of the waveguide but the distal toroid ferrite surfaces arein intimate contact with the narrow waveguide side walls. A biasingmagnetic means including a latching current produces magnetization inopposite directions in the respective spaced proximal toroid ferritesurfaces.

The invention described herein may be manufactured, used, and licensedby or for the Government for governmental purposes without the paymentto use of any royalty thereon.

BACKGROUND OF THE INVENTION This invention relates to microwavetransmission circuits and more particularly to non-reciprocal ferritephase shifting devices for use in microwave transmission circuits.

Magnetic materials in either metallic or insulator forms possess, to alarger or lesser degree, the tendency to remain magnitized, particularlyif the material is in the form of a continuous loop. Such shapes astoroids and hollow cylinders are examples of such loops. In other words,a magnetic field magnetizes the material. After the field is removed aportion of the magnetization remains. Magnetic type ferrites have suchremanent magnetized qualities and accordingly may be said to have asquare loop hysteresis magnetic characteristic.

It is well known to use single full height ferrite toroids in the centerof waveguides propagating microwave energy as non-reciprocal microwaveenergy phase shifters. Such units have proved to be efficient,multistable phase shifters which required relatively low drive power andcompletely eliminated the necessity of steady holding currents. However,the latching wire of such phase shifters is in the position of maximumelectric field and hence is susceptible to breakdown in circumstanceswhere phase shifters of high peak and average microwave power isrequired. Furthermore, intimate contact is required between theinterfaces of the ferrite and the top and bottom broad walls of thewaveguide to prevent possible moding and onset of corona and subsequentbreakdown. It is imperative that no undue pressure be placed on aferrite toroid which is quite magnetostrictive since the remanencemagnetization of the toroid would be affected with pressure due totemperature changes.

SUMMARY OF THE INVENTION It is an object of the present invention toprovide an improved non-reciprocal ferrite phase shifter wherein theabove noted limitations are overcome.

It is yet another object of the present invention to provide an improvednon-reciprocal ferrite phase shifter which is capable of operatingefliciently at relatively high peak power and high average power.

8 Claims 3,524,152 Patented Aug. 11, 1970 ice It is still another objectof the present invention to provide a non-reciprocal ferrite phaseshifter wherein the remanence magnetization of the ferrite is relativelystable with temperature.

In accordance with the present invention there is provided anon-reciprocal microwave energy phase shifter which includes a waveguidesection having broad top and bottom surfaces and narrow side walls. Alsoincluded are a pair of spaced toroid ferrites positioned longitudinallywithin the waveguide section such that the distal toroid ferritesurfaces are in intimate contact with the narrow side walls. Furtherincluded are biasing waveguide means for producing magnetization inopposite directions in the respective spaced proximal toroid ferritesurfaces. The-toroid ferrites are spaced from the top and bottomwaveguide surfaces.

In one embodiment of the invention there is provided a unitary H-beamtype structure for supporting the ferrites in position within thewaveguide section, and with the cross arm of the H-beam structure beinga septum separating the two toroid ferrites. The H-beam structure ismade of a non-magnetic, non-conductive, low loss mate rial having a highdielectric constant and a relatively high coefiicient of thermalconductivity. The side arms of the H-beam structure are spaced from thetop and bottom waveguide surfaces and coplanar therewith.

In another embodiment of the invention, the toroid ferrites areseparated by an I-beam structure intermediate the top and bottomsurfaces of the waveguide, with the toroid ferrites separated by andsupported in the narrowed sections of the I-beam structure.

BRIEF DESCRIPTION OF THE DRAWING For a better understanding of theinvention, together with other and further objects thereof, reference ismade to the accompanying drawing wherein:

FIG. 1 is an isometric drawing, partially cut away, illustrating anembodiment of the phase shifter;

FIG. 2 is a plan view partially in cross section, to illustrate thedirection of magnetic fields in the ferrite toroids; and

FIG. 3 is a plan view, partially in cross section illustrating a secondembodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to FIGS. 1 and 2of the drawing, at 10 there is shown a section of a rectangularwaveguide havingrelatively wide top and bottom surfaces 12 and 14 andrelatively narrow side walls 16 and 18. Intermediate top and bottomsurfaces 12 and 14 and coplanar therewith are a pair of longitudinallydisposed spaced parallel dielectric plates 20 and 22 which arecoextensive with the wide dimension of waveguide section 10. Thedielectric plates 20 and 22 equally spaced from the respective top andbottom surfaces 12 and 14 and are maintained in position withinwaveguide section 10 by means of suitable slots of channels providedtherefor in the narrow side Walls 16 and 18 of waveguide 10. Arelatively narrow rib or septum 24, rectangular in cross section andmade of a suitable dielectric material extends axially through waveguidesection 10 and is integral with dielectric plates 20 and 22 to form asingular H-beam configuration structure. Septum 24 is coplanar withnarrow walls 16 and 18. By such an arrangement two side by sidelongitudinal compartments 26 and 28 are formed within waveguide 10'magnetic, non-conductive, low loss material having a high dielectricconstant and a relatively high coefficient of thermal conductivity. Onesuch material is a doped beryllium oxide known by the trade nameThermalox K. Other materials that may be used are magnesium titanate andboron nitride.

Positioned within compartment 26 and coextensive therewith is a toroid30 of ferrite material, preferably rectangular, and dimensioned suchthat its respective outer peripheral surfaces are in contact with thefour respective walls of compartment 26. Similarly, a toroid 32 offerrite material is positioned in like manner within compartment 28 andcoextensive therewith. Both ferrites are made of identical ferritematerials responsive to microwave RF energy and characterized by asquare loop hystersis magnetic characteristic. One such ferrite is knownin the art as the Al-Dy yig type ferrite. Discrete latching wires 34 and36 extend through compartments 26 and 28, respectively. As shown, wire34 extends longitudinally through compartment 26 close to the innersurface of the wall of toroid 30 which abuts narrow waveguide Wall 18 ofwaveguide 10 and emerges at opposite ends of toroid 30 through holesprovided therefor in narrow waveguide wall 18. Similarly, wire 36extends longitudinally through compartment 28 close to the inner surfaceof the wall of toroid 32 which abuts narrow wall 16 of waveguide 10 andemerges at opposite ends of toroid 32 through holes provided therefor innarrow waveguide wall 16. The terminals of latching wires 34 and 36 areconnected so that the current pulse in both latching wires is in thesame direction when pulsed by a D-C source. This can be readilyaccomplished by connecting the wires 34 and 36 by conductor 38 as shown,and applying a D-C pulse source across the respective free ends oflatching wires 34 and 36. The direction of the current flow is indicatedby the dashed arrow heads. Matching boron nitride transformers as at 40are conventionally provided at both ends of waveguide 10.

For optimum performance at X-band, septum 24 and plates 20 and 22 shouldhave relatively narrow widths, preferably and respectively, about .042"and .025" thick; the air gaps between dielectric plates 20 and 22 andrespective top and bottom waveguide surfaces 12 and 14 are about .050";and the septum 24 and dielectric plates 20 and 22 are made in amonolithic form from material characterized by a high dielectricconstant and a relatively high coefficient of thermal conductivity.Also, a suitable silicone compound may be applied to the interfaces ofthe dielectric septum 24 and the toroids 30 and 32, and the longitudinalslots supporting the dielectric plates 20 and 22 within waveguide 10 maybe coated with a copper loaded silicone grease.

The operation of the phase shifter is best described in connection withFIG. 2. With the latching current in both ferrites in the samedirection, the direction of the bias ing magnetic fields or fiux withineach of the ferrite toroids 30 and 32. is shown to be clockwise so thatthe magnetization is in opposite directions on both sides of septum 24.With such an arrangement, the phase shifter will be non-reciprocal, thatis, the differential phase shift with respect to the dominantpropagating TE mode will be different in one direction than in theother. The degree of phase shift will, of course, depend upon themagnitude and polarity of the D-C pulsing current and the length ofwaveguide 10. For example, with the shown clockwise direction of therespective magnetic fields, the relative state of phase shift may besaid to be for a given magnitude of D-C current pulse. If the D-Ccurrent pulse is reversed, but not necessariliy at the same givenmagnitude, then the respective magnetic fields will be in thecounterclockwise direction and, for example, a 90 differential phaseshift could be achieved. The interaction between the RF magnetic fieldof the TE dominant waveguide mode and the magnetization in the ferritetoroids to produce the differential phase shift of the propagatingelectromagnetic wave is well known in the art and no further explanationthereof is believed necessary. Latching is obtained by using the squareloop hysteresis characteristic of the ferrite material. Thus, after theD-C pulse is removed, the magnetization will follow the square loophystersis curve of the ferrite material so that both ferrite toroids 3i)and 32 will remain magnetized at remanence.

FIG. 3 illustrates another embodiment of the invention. Referring now toFIG. 3, where like numbers refer to like elements, the longitudinalseptum 25 within waveguide lltl has an I-beam configuration and ispositioned intermediate the top and bottom waveguide surfaces 12 and 14.As shown, the ferrite toroids 3t and 32 are positioned and supported oneither side of the septum 25 within the narrowed portions of the I-beamconfiguration. As in FIG. 1, septum 25 is made of a dielectric materialhaving a relatively high coefficient of thermal conductivity and arelatively high dielectric constant. For optimum performance silicongrease is applied to the interfaces of the ferrite toroids 30 and 32 andthe narrowed I-beam walls wherein the ferrites are supported; theferrite toroids 30 and 32 and narrow waveguide walls 16 and 18; and theI-beam septum 25 and top and bottom waveguide surfaces 12 and 14.

We wish it to be understood that we do not desire to be limited to theexact details of construction shown and described, for obviousmodifications will occur to a person skilled in the art.

What is claimed is:

1. A non-reciprocal microwave energy phase shifter comprising awaveguide section having broad top and bottom surfaces and narrow sidewalls, a pair of spaced toroid ferrites positioned side by sidelongitudinally within said waveguide section such that the distal toroidsurfaces are in intimate contact with said narrow walls,

a dielectric septum separating said ferrite toroids along thelongitudinal axis of said waveguide,

and biasing magnetic means for producing magnetization in oppositedirections in the respective spaced proximal toroid ferrite surfaces,

said toroid ferrites being spaced from said top and bottom waveguidesurfaces.

2. The phase shifter in accordance with claim 1 where in said biasingmagnetic means comprises a DC pulse source and a current carrying firstand second wires positioned along respective distal toroid ferritesurfaces, said wires being arranged such that when connected to saidpulse source the latching current in each wire will be in the samedirection.

3. The phase shifter in accordance with claim 1 wherein said dielectricseptum is intermediate said top and bottom surfaces and comprises anI-beam configuration, with said toroid ferrites supported in thenarrowed portion of said I-beam structure.

4. The phase shifter in accordance with claim 2 and wherein saiddielectric septum is intermediate said top and bottom surfaces andcomprises an I-beam configuration, with said toroid ferrites supportedin the narrowed portion of said I-beam structure.

5. The phase shifter in accordance with claim 2 and further a unitaryH-beam structure made of dielectric material, the cross bar of saidH-beam structure being said septum separating said toroid ferrites, andthe respective side arms of said H-beam structure being positioned andparallel with said top and bottom waveguide surfaces, respectively, andspaced therefrom.

6. The phase shifter in accordance with claim 5 and further includingchannels in said narrow waveguide walls for maintaining said H-beamstructure in position within said waveguide.

5 6 7. The phase shifter in accordance with claim 5 where- FOREIGNPATENTS in the unitary H-beam structure is made of non-magnetic 1 4 9 91o 96 non-conductive, low-loss material having a high dielectric 5 72 /16 Fi constant and a relatively high coefficient of thermal con- OTHERREFERENCES ductivity.

8. The phase shifter in accordance with claim 3 where- 5 R 'w g 9 g g min the I-beam structure is made of non-magnetic, nonec angu at avegul one wary conductive, low-loss material having a high dielectric com 196787 relied stant and a relatively high coeflicient of thermal conduc-PAUL L GENSLER Primary Examiner tivity.

References Cited 10 CL XJL UNITED STATES PATENTS 333-98 3,425,003 1/1969Mohr 33324.1 X

3,435,382 3/ 1969 Agrios et al 333-24.1 X

